Clamping or braking devices of very diverse designs are used for very diverse applications. For example, European Publication No. EP-A-0936366 describes a braking device for a linear guide with a support body that is movable along a guide rail. The support body has brake shoes that act on the two long sides. The support body is constructed in an H-shape and has a thin, elastically flexible web and two lower legs with which it reaches around the guide rail. A brake shoe is arranged between each leg and the guide rail. The support body is furnished with two upper legs which, together with the web, form a holding space in which a force-generating means acting on the upper legs is provided. This can be a hydraulically or pneumatically actuatable knee lever mechanism or a piezo actuator. A hydraulically or pneumatically actuatable tapered slide valve that is guided, in a space formed for this purpose and tapering in the direction of the braking device, between the upper legs of the support body can also be provided as a force converter. In all cases, the elastic web bends due to the application of force to the two upper legs, so that the two lower jaws with the brake shoes are moved inwards and apply a greater force to the guide rail.
In this known braking device, used with an electromechanical converter such as a piezo element, the sensitivity of the latter to shocks or other mechanical stresses is particularly disadvantageous.
The use of a knee lever mechanism or a tapered slide valve implies a high assembly or manufacturing cost just like that for an electromechanical converter.
Additionally there is the need, particularly in the case of clamping devices, for relatively high clamping forces that can be achieved in known devices only with a relatively great construction effort and therefore high costs.
Another example design is found in U.S. Pat. No. 5,855,446, which describes a hydraulic clamp bushing that is aligned with a shaft and can be connected to it in torque-proof fashion. The bushing has a substantially stable bushing body, which is arranged around a driveshaft a distance therefrom. A chamber which can be subjected to pressure is provided adjoining this bushing body and facing the shaft. A side wall of this chamber extending substantially parallel to the shaft simultaneously serves as a braking element, which is pressed against the shaft due to the expansion of the chamber when the chamber is acted upon by pressure in order thereby to produce a frictional connection. A Σ-shaped formation of the laterally adjoining walls of the chamber is intended to prevent the bushing from being oriented at a slant to the shaft when the chamber is acted upon by pressure. The Σ-shaped side walls of the chamber allow an expansion of the side walls radially toward the shaft in case pressure is applied, even before the increasing chamber pressure also presses the chamber wall running parallel to the shaft against the shaft. Thus, the bushing can orient itself perpendicular to the shaft axes before the rotationally fixed connection is produced.
This clamping device does not have a favorable force transmission for generating high pressing forces. Moreover, the chamber is limited in its shape and, in particular, in its possibilities for arrangement relative to the bushing body. Braking force can be achieved here only by application of positive pressure, and the actual braking element, which may have to transfer high drive forces, is not connected fixedly to the bushing body, but only via the necessarily relatively unstable pressure chamber.
Another known device is found in PCT Publication No. WO 01/34990 A1, which describes a clamping or braking device in which a chamber that can be subjected to pressure and is delimited in at least a partial area by at least one flexible tension-resistant or pressure-resistant wall, is provided on a base element. The boundary of the chamber opposite the wall can be designed like the first wall. It can also be a rigid part of a body, however. The walls are preferably a relatively slight distance apart. The forces resulting from the deformation of the chamber are directed at least in part in the direction of or along the wall, and are directed into the base element in the area of its connection to the wall. If one suitably selects the impingement point of such forces on the base element, and if this base element is at least partially deformable, then the forces can be transmitted via this base element to other parts of the base element, for example, into clamping or braking areas. A corresponding braking or clamping means in these areas can then be moved by means of the forces into an impingement position or out of the latter, in order to brake or release an element to be clamped or braked. Both applied positive and negative pressure in the chamber can be used here in order to introduce both tensile and compressive forces into the base element. Naturally, the clamping or braking areas can still be engaged with the guide element or the element to be clamped or braked before and after the force introduction, in which case however, changes of the impinging forces between the clamping or braking areas and the respective other element result.
This known clamping or braking device proceeds from the recognition that a suitable chamber seeks a deformation when acted upon by negative or positive pressure. If this chamber is formed to a large degree by at least one approximately flat wall, then positive or negative pressure in the chamber initially causes a deformation in a first direction that runs substantially perpendicular to this wall. In order to yield to the deformation (expansion or contraction) in this first direction, there is a corresponding contraction or expansion of the chamber in a second direction running generally perpendicular to the first direction (i.e., substantially parallel to the wall). This makes use of the fact that slight forces or deformations in the first direction produce large forces in the second direction, which can be used for braking or clamping, or for releasing pretensioned clamping or braking devices.
Finally, an expansion chuck device is known from PCT Publication No. WO 2005/044491 A1, which has a base element with a thin-walled expansion bushing provided on an axial end area of the base element and forming a central receptacle for a component to be clamped. Also provided is a clamping ring which surrounds the expansion chuck, forming an annular pressure chamber therebetween, and which is screwed to the base element. The pressure chamber is filled with a hydraulic means. The expansion bushing can be elastically deformed in order to fix a component in the receptacle. For this purpose, the clamping ring is displaced by rotation relative to the base element, reducing the volume of the pressure chamber. The hydraulic means in this expansion chuck is implemented as an elastic solid body. A sliding ring element is arranged between the elastic solid body and a pressure surface of the clamping ring in order to transmit an axial compressive force from the clamping ring to the solid body. By using the sliding ring, purely axial compressive forces are introduced onto the solid body, and their axial movement is decoupled from the rotational movement of the clamping ring.
This expansion chuck device, however, only allows the clamping of a rotationally symmetrical body by means of the annularly shaped solid body serving as a hydraulic means. What is needed, therefore, are clamping devices that allow flexible adaptation to a variety of clamping tasks.